anagram: Clarify expectations about identical words

An anagram is defined as

1. the same letters
2. rearranged
3. to make a new word

The existing assertion only checked the presence of the expected word,
but did not explicitly exclude the existence of results that match the
input exactly.

anagram/src/test/java/AnagramTest.java

     public void testIdenticalWordIsNotAnagram() {
         Anagram detector = new Anagram("corn");
         List<String> anagrams = detector.match(Arrays.asList("corn", "dark", "Corn", "rank", "CORN", "cron", "park"));
-        assertThat(anagrams, hasItems("cron"));
+        assertEquals(anagrams, Arrays.asList("cron"));
     }
 
     @Test